1. Field of the Invention
The present invention relates to a liquid crystal array inspection apparatus and a beam scanning apparatus for inspecting a liquid crystal substrate array based on a scan image acquired by scanning the substrate in a two-dimensional manner, using a charged particle beam, such as an electron beam or ion beam.
2. Description of Related Art
A known substrate inspection apparatus applies an inspection signal to an object to be inspected, such as a liquid crystal substrate array, and performs substrate inspection based on a scan image acquired by scanning the substrate in a two-dimensional manner with a charged particle beam, such as an electron beam or ion beam. For example, in the manufacturing process of a Thin Film Transistor (TFT) array substrate used in a TFT display apparatus, whether the manufactured TFT array substrate is correctly driven is being inspected. In the inspection of the TFT array substrate, an electron beam, for example, serving as a charged particle beam is used to scan the TFT array substrate so as to acquire a scan image and the substrate is inspected based on the scan image (Patent Document 1 and Patent Document 2).
In order to enable the electron beam to scan the array in a two-dimensional manner on the liquid crystal substrate, the electron beam is moved to-and-fro in an X direction, and a stage is moved in a Y direction.
For a scanning accomplished by the application of the electron beam and a movement of the stage, it is difficult to achieve a high precision scanning with a scan width of an electron beam emitted by a single electron gun. Accordingly, the entire scan range of a substrate is divided into a plurality of portions, and an electron gun is mounted at each portion. Furthermore, the following control method is used, in which the scan range of each electron gun is divided into a plurality of paths arranged in the X direction, and in each path, the translocation of the stage by a translocation width equivalent to a width of one pixel of the liquid crystal substrate in the Y direction and the scanning with a beam having a scan width equivalent to a width of one pixel in the X direction are alternately performed, so as to acquire a scan image along the path.
FIG. 13(a) to FIG. 13(c) are views illustrating the scanning of a liquid crystal substrate using electron beams. In FIG. 13(a) to FIG. 13(c), a plurality of electron guns (GUN1, GUN2, etc.) is disposed in the X direction of the liquid crystal substrate at a specified interval, and the electron gun emits an electron beam onto the liquid crystal substrate. During the emission of the electron beam, each electron gun scans with the electron beam having a scan width Dx in one of a plurality of paths (Path 1 to Path 4 in FIG. 13(a) to FIG. 13(c)) allocated on the liquid crystal substrate. Through the moving to-and-fro operation of the electron beam of the electron gun, the electron beam scans in a unit of a path; after one path is scanned, the stage is moved so as to scan a neighboring path. When the stage is moved, the stage is only moved by a stage-movement-width Lx, which is equivalent to the width of the path.
FIG. 13(b) illustrates a scan state of Path 1, in which the stage is moved only the stage-movement-width Lx from the scan position of Path 1 shown in FIG. 13(a), and Path 2 is scanned through the movement. In addition, FIG. 13(c) illustrates the situation that the stage is moved only the stage-movement-width Lx from the position of FIG. 13(b), and Path 3 is scanned. As such, all the paths set on the liquid crystal substrate are scanned.
During the scanning of each path, an inspection signal is applied to the liquid crystal substrate, and the liquid crystal substrate array is scanned by the electron beam and secondary electrons are detected, so as to acquire a detection signal. One path is divided into a plurality of frames, and the inspection signal is applied to each frame and the detection signal is detected. The inspection signal is applied in all the paths and the detection signal is detected, and the scan images acquired in each scanning are combined, so as to obtain a scan image of the entire substrate.
Moreover, the application of the inspection signal, the scanning with the electron beam and the detection of secondary electrons are performed for multiple times (for example, 20 times) for each frame, so that a plurality of the acquired detection signals overlaps and the signal strength of the detection signal can be increased.    Patent Document 1: Japanese Laid-open Patent Publication No. 2004-271516    Patent Document 2: Japanese Laid-open Patent Publication No. 2004-309488
A plurality of scan images is combined to obtain a scan image of the liquid crystal substrate, and the scan image is acquired by scanning with electron beams from a plurality of electron guns configured in a row in the X direction of the liquid crystal substrate. The electron guns are configured at intervals in a row in the X direction, and the emission angle of the electron beam emitted by each electron gun or other conditions of the electron beam may be inconsistent. Therefore, the imaging range obtained by each electron gun in the X direction may be displaced.
In the case that displacement of the imaging range in the X direction occurs, when a plurality of imaging ranges is combined, an area in the X direction may not be imaged.
In addition, the electron guns arranged in the X direction of the liquid crystal substrate is configured as multiple rows in the Y direction, so that the scanning time for scanning one liquid crystal substrate is shortened. Thus, it is anticipated that the time for inspecting the liquid crystal array can be reduced.
In the structure in which the electron guns are configured in multiple rows as described above, not only the imaging range obtained by the electron guns arranged in each row may be displaced, a displacement may also occur between the rows of the neighboring imaging ranges in the Y direction.
In the case the imaging range in the Y direction is displaced, an area in the Y direction may not be imaged when a plurality of imaging ranges is combined.